Recurrent Thioperazine-Induced Extrapyramidal Reaction Following Placebo Substitution for Maintenance Antiparkinson Drug

A placebo was abruptly substituted for maintenance antiparkinson drug in 20 patients who had previously shown evidence of a thioperazine-induced extrapyramidal reaction. Within 20 days of this controlled study extrapyramidal reactions reappeared in 16 patients (80%). The recurrence rate of phenothiazine-induced extrapyramidal reactions following withdrawal of maintenance antiparkinson drug will vary with different situations and their incidence can only be determined by clinical trial.